A system including a transducer and an amplifier as well as a circuit which always has a high impedance at low voltages. In addition, at high voltages, the circuit has a high impedance at high frequencies but a low impedance at low frequencies. In biased transducers, this circuit may be used between the charge pump and the transducer. In general, the circuit may be provided in a signal path between the transducer and the amplifier. The circuit has as an advantage that at startup, low frequency signals at high intensities may overload the amplifier, whereas at operation, higher frequency signals are desired fed to the amplifier at the same intensity. This is facilitated by the circuit.